The reforming of petroleum raw materials is an important process for producing useful products. For example, reforming processes may be utilized for separating and upgrading hydrocarbons to provide a transportation fuel, such as producing a naphtha feed stream and upgrading the octane value of the naphtha from the production of gasoline. Additionally, hydrocarbons in feed streams from a raw petroleum source may also be utilized the production of desired chemical precursors for use in the production of plastics, detergents and other products. Accordingly, reforming may be used to produce the desired chemical precursors.
The catalytic reforming process is well known in the art. The principal reactions that take place are the dehydrogenation of naphthenes to aromatics, dehydrocyclization of paraffins, isomerization of paraffins and naphthenes, hydrocracking of paraffins to light hydrocarbons, and formation of coke which is deposited on the catalyst. The formation of coke on the catalyst causes the catalyst to gradually lose activity over time. Accordingly, the catalyst requires regeneration and/or replacement. A continuous transfer of catalyst from and to the reactor is highly desirable.
Typically, in such a reactor, a hydrocarbon feedstock and a hydrogen-rich gas are preheated and charged to a reforming zone containing typically two to five reactors in series. The effluent from the first reactor is withdrawn, heated, and passed to the second reactor. The effluent from the second reactor is withdrawn, reheated and passed to the third reactor. The withdrawal and reheating of the effluent continues until the last reactor and is typically referred to as a radial flow. From the last reactor, the effluent is withdrawn and processed further.
The feedstock/partially converted effluent streams are often passed into the reactor stack via non-reactive sections. Catalyst flows downward through the non-reactive sections in conduits so as to avoid contacting the feedstock/partially converted effluent streams in the non-reactive zones. This empty space is required for meeting the hydraulics requirements in some reactors. In other reactors, the space is required for the reactor inspection, maintenance, and repair. The empty space contains mechanical parts like catalyst transfer pipes, mechanical supports, and process lines. For incoming flow, this will cause flow impingement that results in unequal process gas distribution to the circumference of the reactor. This ultimately results in lower yields and lower utilization of the reactive zone.
Thus, there is an ongoing desirability desire to provide solutions which effectively and efficiently distribute the process gas within the non-reactive zone while maintaining appropriate flow pressure drop of the fluids flowing therein.